Merge Three Sorted linked lists
Last updated: January 30, 2026
Quick Overview
Given three sorted linked lists, merge them into a single sorted linked list. The input consists of the heads of the three linked lists, and the output should be the head of the newly merged linked list, maintaining the sorted order.
Meta
January 30, 202680
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258 solved
Given three sorted linked lists, merge them into a single sorted linked list. The input consists of the heads of the three linked lists, and the output should be the head of the newly merged linked list, maintaining the sorted order.
Coding interviews at Meta focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
What the Interviewer Expects
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would you modify your solution to handle streaming input?
- What if the input doesn't fit in memory?
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Problem Analysis
To merge three sorted linked lists into one sorted linked list, we can utilize the 'two pointers' technique, particularly extending it to handle three pointers (one for each list). This approach is ap...
Approach
- Initialize three pointers, one for each linked list (let's call them
l1,l2, andl3). - Create a dummy node to facilitate easier list merging, and maintain a
currentpointer to build the n...
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